1. Field of the Invention
The disclosure generally relates gate valves. More particularly, the disclosure relates to the expanding gate valves.
2. Description of the Related Art
A type of gate valve known as a “through-conduit” gate valve provides a full bore, unbroken passageway when the valve is fully open. To seal the valve, a gate assembly moves transverse to the flow passageway to open and close flow through the passageway by sealing against seats surrounding the passageway disposed generally upstream and downstream of the gate assembly. A gate assembly for a through-conduit valve typically is an elongated assembly having a flow opening (“port”) in a lower portion and no port in an upper portion. To open the valve, the gate assembly is raised into an upper housing of the valve body to align the port in the lower portion of the gate assembly with the flow passageway through the valve body to allow flow. To close the valve, the gate assembly is lowered into a cavity below the flow passageway to align the upper portion without the port with the flow passageway.
To allow the gate assembly movement, a clearance between seats and the gate assembly is useful during movement, but detrimental in a closed position to effect a seal. To accommodate the change in clearance, an expanding gate assembly has been used in the industry. A gate of the gate assembly is coupled with a segment of the gate assembly that interfaces with the gate typically along a tapered surface. The gate assembly can expand in overall thickness in the closed position to fill the clearance to seal against the seats, but collapse in overall thickness when opening to allow the gate assembly to move. Through-conduit gate valves rely on the gate assembly to retain the seats in position. Through-conduit gate valves can also rely on seat plates to retain the seats in position.
The WKM Powr-R-Seal valve, illustrated in U.S. Pat. No. 2,583,512, is an example of a through-conduit gate valve with seats, seat plates, and an expanding gate assembly. Using the nomenclature and element numbers from such patent, the gate assembly, having a gate 25 and a segment 26, slides between seats 14, 15 and seat plates 17, 18 with side flanges 19, 20 that extend below the flow passageway, so that the gate assembly is supported in a closed position and an open position. The seat plates extend transverse to the flow passageway and can be integral to the seats against which the gate assembly seals across the flow passageway.
Such a configuration is not acceptable in a non-ported gate valve. There is no cavity below the flow passageway in which to lower a gate assembly with the port. Thus, a gate assembly in a non-ported gate valve does not have the lower portion with the port.
FIG. 1A is an exemplary prior art side view schematic of a through-conduit gate valve portion. FIG. 1B is an exemplary prior art front view schematic of the through-conduit gate valve portion of FIG. 1A. FIG. 2A is an exemplary prior art side view schematic of a non-ported gate valve portion. FIG. 2B is an exemplary prior art front view schematic of the non-ported gate valve portion of FIG. 2A. The figures will be described in conjunction with each other. Referring to FIGS. 1A and 1B, a through-conduit gate valve portion 45 includes an upper portion 46 and a lower portion 47. The upper portion 46 is blocked without a port and the lower portion 47 includes a port 48. In contrast, referring to FIGS. 2A and 2B, a non-ported gate valve portion 44 includes an upper portion 46 without the lower portion 47 or the port 48, significantly shortening the gate assembly. A guide 49 shown in FIG. 1A that would typically be positioned in a lower cavity of a through-conduit valve is not available for a non-ported valve because the non-ported valve does not have a sufficiently long lower cavity. Further, the guide 49 for the through-conduit gate valve portion would not adequately support the shorter non-ported gate valve portion 44 for a non-ported gate valve when in the raised open position. Simply extending the guide 49 upward in the orientation shown is problematic due to mechanical stops employed in the valve function.
A further complication can be evidenced from comparing the FIGS. 1A-1B to FIGS. 2A-2B. In a through-conduit valve using the through-conduit gate valve portion 45, either the upper portion 46 or the lower portion 47 would support the seats in position around a valve flow passageway disposed in the valve body depending on whether the valve is closed or open. However, for the non-ported valve, using the non-ported gate valve portion 44 without a lower portion, the seats will be unsupported when the upper portion is moved upward and the valve is open, a time when the support is much needed. To restrain the seats in position for a non-ported gate valve, U.S. Pat. No. 4,017,058 supplies retainers with hook portions that hooks into a specially formed groove.
An example of a compact expanding gate valve is shown in U.S. Pat. No. 6,164,622. As illustrated in the figures and described in the Abstract of that patent, the compact expanding gate valve 10 has a valve body 12 defining a flowway 18, 20 and having spaced internal seat rings 72, 74. Guide elements (pins 106, 108 in FIGS. 1-4 or rib-like guide element 111 in FIG. 5) are fixed in position to the valve body and project internally from the valve body. A valve stem driven gate and segment assembly 80 is movable within the valve body between open and closed positions relative to the seat rings and has control arms 116 mounted by actuating pins 112, 114 to each side of gate member 82 and segment 90 of the gate and segment assembly. The control arms 116 each have an arm section 118 separated from an opposing arm section 120 by a guide slot 122. The guide slot 122 enlarges at a top portion of the control arm into a slot enlargement 128. The control arms 116 are not fixed but rather are movable linearly with the gate and segment assembly 80 and are disposed in guided relation with the fixed guide elements 106, 108 (or 111) during opening and closing movement. During initial movement of the gate and segment assembly 80 from the closed position, the pinned connection of the control arms 116 to the gate member 82 and the segment member 90 causes the control arms to pivot responsive to relative linear movement of the gate and segment members and apply collapsing force to the gate and segment members to collapse the gate and segment assembly to minimize frictional contact thereof with the seat rings and permit its movement by the valve stem from the closed position to the open position. However, among other aspects, the configuration of the guide elements 106, 108 (or 111) do not show any contact with the seat rings 72, 74 to hold the seat rings in position when the gate assembly 80 is upward and the valve is open.
Thus, there remains a need for providing a design for a non-ported gate valve that employs an expanding gate assembly.